P-doped all-small-molecule organic solar cells with power conversion efficiency of 17.73%

All-small organic solar cells (ASM OSCs) inherit the advantages of the distinct merits of small molecules, such as well-defined structures and less batch-to-batch variation. In comparison with the rapid development of polymer-based OSCs, more efforts are needed to devote to improving the performance of ASM OSCs to close the performance gap between ASM and polymer-based OSCs. Herein, a well-known p-dopant named fluoro-7,7,8,8-tetracyano-p-quinodimethane (FTCNQ) was introduced to a high-efficiency system of HD-1:BTP-eC9, and a high power conversion efficiency (PCE) of 17.15% was achieved due to the improved electrical properties as well as better morphology of the active layer, supported by the observed higher fill factor (FF) of 79.45% and suppressed non-radiative recombination loss. Furthermore, combining with the further morphology optimization from solvent additive of 1-iodonaphthalene (IN) in the blend film, the HD-1:BTP-eC9-based device with the synergistic effects of both FTCNQ and IN demonstrates a remarkable PCE of 17.73% (certified as 17.49%), representing the best result of binary ASM OSCs to date.[Figure not available: see fulltext.].